symfony/src/Symfony/Component/Validator/Constraints/RegexValidator.php

<?php

namespace Symfony\Component\Validator\Constraints;

use Symfony\Component\Validator\Constraint;
use Symfony\Component\Validator\ConstraintValidator;
use Symfony\Component\Validator\Exception\UnexpectedTypeException;

class RegexValidator extends ConstraintValidator
{
    public function isValid($value, Constraint $constraint)
    {
        if ($value === null) {
            return true;
        }

        if (!is_scalar($value) && !(is_object($value) && method_exists($value, '__toString()'))) {
            throw new UnexpectedTypeException($value, 'string');
        }

        $value = (string)$value;

        if (
            ($constraint->match && !preg_match($constraint->pattern, $value))
            ||
            (!$constraint->match && preg_match($constraint->pattern, $value))
        )
        {
            $this->setMessage($constraint->message, array('{{ value }}' => $value));

            return false;
        }

        return true;
    }
}